Comparison between air-core and laminated iron-core inductors in filtering applications for switching converters

Inductors for filtering devices are widely employed in power electronics applications in order to reduce voltage and current harmonics caused by switching converters. The use of ferrite-core inductors is limited to small power applications, whereas air-core and laminated iron-core inductors are employed in the medium-to-high power range. The choice of the core medium strongly affects the behavior of the inductor versus frequency. In particular, the inductance, the self-resonant frequency, the winding and core losses and the stray magnetic field are quite different for air-core and laminated iron-core inductors. In this paper a comparison between these two kinds of inductors is carried out through an analytical approach and experimental validations.